1. Field of the Invention
The present invention relates generally to wireless communication and, more particularly, to a channel estimation method and apparatus using a data channel in a wireless communication system that is capable of improving channel estimation accuracy by adjusting a data channel utilization ratio based on a bit error rate of the data channel.
2. Description of the Related Art
In high-speed wireless communication systems, Inter-Symbol Interference (ISI) caused by channel distortion or multipath propagation is a main cause in the obstruction of reliable communications. Therefore, recent wireless communication systems are preferably based on Code Division Multiple Access (CDMA) and Orthogonal Frequency Division Multiplexing (OFDM) due to their ability to prevent ISI.
In the CDMA or OFDM-based wireless communication system, channel estimation is performed in order to compensate for signal distortion on the channel. There are two categories of channel estimation algorithms, namely, Pilot Symbol Aided Channel Estimation using training symbols (i.e., pilot symbols) known to the receiver and Decision Directed Channel Estimation using data symbols and pilot symbols.
The Decision Directed Channel Estimation algorithm utilizes both the pilot symbols and the data symbols under the assumption that the decided data symbols are accurate and can be used as training symbols. In principle, in the absence of transmission error, the high availability of pilot information can be used. Thus, a superior estimation result is expected as compared to the Pilot Symbol Aided Channel Estimation algorithm.
However, since the hard decision value of the data channel is used in the conventional Decision Directed Channel Estimation algorithm, the symbols of the erroneous data channel can act as interference with a low active Signal to Noise Ratio (SNR). Particularly, when the Bit Error Rate (BER) is high, the channel estimation performance can be degraded significantly, and worse than that of the Pilot Symbol Aided Channel Estimation algorithm.